In other online posts, they threatened to kill Australian soldiers and all non-Muslims.

Attorney-General George Brandis described the Australians who have joined ISIL as the biggest threat to Australian national security.

"What they have demonstrated is a promotion of violent crimes, probably war crimes," Attorney-General George Brandis told the ABC's 7:30.

A spokeswoman for the Australian Federal Police said the pair would be arrested immediately for terrorism-related offences if they returned to Australia.

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However, a friend of the pair told Fairfax Media they have no intention of ever returning.

"They say they've never lived a better life than what they’re living now and 'you don't know what youse are missing out on, especially with the turn of events happening now [with the establishment of a caliphate in Iraq]," said the friend, who didn't want to be identified.

"People say they're worried these guys will come back but they understand that if they leave the country to go to Syria or Iraq they're not coming back. They're after two things - victory for Islam or martyrdom."

Mohammed Elomar's latest twitter post reveals that he may have briefly stopped being in direct conflict.

Jihad needs patience ! Being on the side Line and watching all the victorys by the mujahideen of Khalifah is a killing me